Acrolein polymers and their biocidal properties have been described by Melrose et al in international publication WO 88/04671. These polymers (referred to as the subject polymers) have a repeating unit of formula I
; or this unit in its hydrated, hemi-acetal or acetal form, represented by the formulae:
wherein R is hydrogen and n is an integer of one or more, have been demonstrated previously. German Patent Application P4404404 and equivalents such as EP667358 and AU 11686/95 (now lapsed) discloses a process in which acrolein is polymerized in an aqueous sodium hydroxide medium. The disclosure states that the resulting polyacrolein is soluble in polyhydric alcohol at 40 to 50° C. to form a solution of the polyacrolein in a polyhydric alcohol. As explained below the assignee of this German application subsequently found such polymers to be problematic and have low solubility in aqueous media.
International Patent Publication WO 96/38186 discloses a process for preparation of poly(2-propenal, 2-propenoic acid) wherein the aldehyde groups of poly(2-propenal) syn polyacrolein are partially auto-oxidised to carboxyl groups, by heating the dry polymer in air, to 100° C. and preferably to between 80° C. and 100° C. The poly(2-propenal, 2-propenoic acid) polymers typically contain 0.1 to 5 moles of carboxyl groups per kilogram. The resulting polymers have significantly improved solubility in dilute aqueous bases, for example aqueous sodium carbonate.
European publication No. 792895 Werle et al (corresponding to U.S. Pat. No. 6,060,571) relates to acrolein releasing polymers prepared by copolymerisation of acrolein monomer and a polyhydric alcohol. Werle et al observe that the polyacroleins described in German Application No. P4404404 are problematic in that the yield is less than desired and the polymers are virtually insoluble in water. European Application 792895 teaches that these problems are overcome by forming an acrolein releasing polymer by copolymerisation of acrolein monomer and a polyhydric alcohol monomer. The proposed structure of the copolymer is as follows:

While free acrolein acts as an antimicrobial it is irritating to the eyes, lungs, tissues and skin. There is a need in a range of applications including on skin and in gastrointestinal treatments for antimicrobials which are stable, highly water soluble, and safe to use.